There are several basic approaches for utilization in music synthesizers. One basic approach is to utilize a musical instrument as a source to derive a tone from the instrument and thereafter process the signal representing the tone to strip the tone of various harmonics to derive a fundamental which is modulated by the musician, all for the purpose of reconstructing various and sundry harmonics through the use of analog circuitry. Such a system is primarily analog in nature. Imagine such a system used with a string instrument, woodwind, reed or brass source. It may form an output signal with ample coloring distinctive of the particular instrument; nevertheless, the coloring is stripped away, and only a fundamental tone is left. The fundamental may range high or low depending on the range achieved by the instrument in question. The musical instrument's distinctive quality remains in that the fundamental is shaped or modified as, for instance, by changes in frequency or pitch, change in fundamental amplitude at the moment of attack, decay of the note and so on. The fundamental is then passed through various and sundry harmonic generators. The harmonic generator can typically form various harmonics, and they are then passed through an adding circuit, the net result being a composite waveform which has been voiced to a specified mix. Certain arbitrary decisions can be made, such as the decision to repress even numbered harmonics. This lends a certain kind of voicing or timbre to the output signal.
Other types of synthesizers are known, including those which utilize an oscillator as a tone source as opposed to a musical instrument. Electronic keyboard insruments typify this approach. This approach, however, is deficient in several regards. Among others, it can never quite accomplish a totally realistic duplication of a given natural instrument's timbre as a stand-alone unit, perhaps being satisfied with only a surrealistic effect. It is simpler in some regards than the analog circuitry of the above mentioned synthesizer. It is fairly difficult to overcome the surrealistic effect when the goal is to precisely duplicate a given instrument (representative). Moreover, such apparatus is still faced with certain arbitrary limits or tradeoffs. As an example, imagine an oscillator signal source functioning as the basic tone generator from which electronic synthesis is accomplished. The signal output, and, hence, the timbre, attack, vibrato, pianissimo, tremolo and the like, must be imposed on the oscillator source. Fortunately, these things are easily imposed on musical instruments by the musician, himself, through the talents developed in his playing ability.
The present invention is markedly different. The present invention is an electronic music synthesis system which is substantially digital in operation. In other words, it utilizes digital circuitry components to handle a monotonic source (for ease of explanation) to produce a digital synthesizer which operates in real time with any kind of input source, including conventional musical instruments. The input frequency source thus preserves the qualities that characterize music as such, including player initiated vibrato, tremolo, pianissimo and the like. A simple transducer serves as an input source and supplies a monotonic note signal. The apparatus thus rolls off some of the harmonics through filters which suppress the higher frequencies to provide a reasonably well defined fundamental frequency and controlled amplitude. The fundamental frequency will carry with it all of the necessary constituent musical qualities which identify real or naturally occurring music in the conventional sense. In other words, the mode of attack and the ending of a given note are preserved. Vibrato and tremolo of the note are preserved. Note intensity or loudness is preserved. Transition from a first note to a second note is also preserved. A synthesized output is achieved with negligible time delay so that the device can truly be described as operating in real time. Real time is substantially no time lag as determined by the ear of a musician.
The present invention has certain advantages over the prior art devices. One advantage is that the qualities of the natural instrument are preserved as mentioned above. If an excess of data information is stripped away from the input signal, the qualities distinctive of the source are lost. This approach is clearly better than the use of an oscillator as a tone source. Moreover, the use of digital circuitry provides a less expensive circuit. Further, digital circutiry has the virtue of functioning well or not functioning at all in contrast with analog circuitry which degrades slightly and gradually over a period of time. Through the use of the digital circuitry herein disclosed, the circuit is able to preserve the primary waveform generator characteristics to either duplicate or modify the distinctive timbre of a specified instrument. Accordingly, it can be used in the sense of providing duplication or voicing to another quality. Duplication can occur as in the example of a musician playing a six-string guitar, where the output would resemble that of a twelve-string guitar. Alternately, a chorus effect can be achieved whereby a single musician is, in effect, provided with a second chair musician, even though one is not physically present. Another mode of expression can be achieved whereby a soloist receives an accompaniment from an instrument of an entirely different family, as, for instance, accompaniment of a brass instrument by a reed instrument, if the device were so voiced. Fortunately, the rules which describe the audio distinctives of brass instruments versus woodwinds are well known. The distinctives of other musical instruments are also reasonably well known, speaking in global terms, and these distinctives can be implemented by this apparatus.
It is with the foregoing in mind that the present invention has been devised. It particularly lends itself to the kind of voicing mentioned above.